A wide variety of processes use radial flow reactors to provide for contact between a fluid and a solid. The solid usually comprises a catalytic material on which the fluid reacts to form a product. The processes cover a range of processes, including hydrocarbon conversion, gas treatment, and adsorption for separation.
Radial flow reactors are constructed such that the reactor has an annular structure and that there are annular distribution and collection devices. The devices for distribution and collection incorporate some type of screened surface. The screened surface is for holding catalyst beds in place and for aiding in the distribution of pressure over the surface of the reactor to facilitate radial flow through the reactor bed. The screen can be a mesh, either wire or other material, or a punched plate. For either a fixed bed or moving bed, the screen or mesh provides a barrier to prevent the loss of solid catalyst particles while allowing fluid to flow through the bed. In a moving bed, solid catalyst particles are added at the top, and flow through the apparatus and removed at the bottom, while passing through a screened-in enclosure that permits the flow of fluid over the catalyst. In a fixed bed, the catalyst, or adsorbent, is loaded into a bed between screens, or other retention devices, and the screens allow fluid to flow over the catalyst while holding the catalyst in place. The screen is preferably constructed of a non-reactive material, but in reality the screen often undergoes some reaction through corrosion, and over time problems arise from the corroded screen or mesh.
One type of screen is a profile wire screen, where a profile wire is wrapped around supports and set at a predetermined spacing for the wire as it is wrapped around the supports. The screen is then cut and flattened and then re-rolled or re-shaped. The screen is shown in U.S. Pat. Nos. 2,046,458 and 4,276,265. The screen can be used as part of an inlet distribution device, or other device for containing a catalyst. One type of inlet distribution device is a reactor internal having a scallop shape and is described in U.S. Pat. Nos. 6,224,838 and 5,366,704. The scallop shape and design provides for good distribution of gas for the inlet of a radial flow reactor, but uses screens or meshes to prevent the passage of solids. The scallop shape is convenient because it allows for easy placement in a reactor without concern regarding the curvature of the vessel wall. The screens or meshes used to hold the catalyst particles within a bed are sized to have apertures sufficiently small that the particles cannot pass through.
The design of reactors to overcome these limitations can save significantly on downtime for repairs and on the loss of catalyst, which is a significant portion of the cost of processing hydrocarbons.